how many  molecules of water are in 72 grams sample

To determine how many molecules of water are in a 72-gram sample, we can follow these steps:

1. **Calculate the molar mass of water (H₂O):**  
   - The atomic mass of hydrogen (H) is approximately 1 g/mol, and there are 2 hydrogens in each water molecule.
   - The atomic mass of oxygen (O) is approximately 16 g/mol.
   \[
   \text{Molar mass of H₂O} = 2 \times 1 + 16 = 18 \, \text{g/mol}
   \]

2. **Determine the number of moles of water in 72 grams:**  
   \[
   \text{Moles of H₂O} = \frac{\text{mass of sample}}{\text{molar mass}} = \frac{72 \, \text{g}}{18 \, \text{g/mol}} = 4 \, \text{mol}
   \]

3. **Calculate the number of molecules:**  
   Using Avogadro's number, \( 6.022 \times 10^{23} \) molecules per mole, we can find the total number of molecules:
   \[
   \text{Number of molecules} = 4 \, \text{mol} \times 6.022 \times 10^{23} \, \text{molecules/mol} = 2.4088 \times 10^{24} \, \text{molecules}
   \]

So, there are approximately \( 2.41 \times 10^{24} \) molecules of water in a 72-gram sample.

Would you like more details or have any questions?

Here are 5 related questions for further practice:
1. How many molecules are in a 36-gram sample of water?
2. What is the mass of 2 moles of water?
3. How many moles are in 90 grams of water?
4. What is the molecular weight of carbon dioxide?
5. How many molecules are in 18 grams of water?

**Tip:** When converting grams to molecules, always find the number of moles first by using the substance's molar mass!

how many molecules of water are in 72 grams sample

Learn how to calculate the number of water molecules in a 72-gram sample. This step-by-step guide covers the mole concept, molecular mass, and the use of Avogadro's number, perfect for students in Grades 9-11.

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